1. Field of the Invention
The present invention generally relates to a method and an apparatus for braking a vehicle and more particularly, to a method and an apparatus which allows a vehicle to be both regeneratively and frictionally braked, thereby allowing the vehicle to be braked in a desired manner while concomitantly allowing energy to be conserved.
2. Background of the Invention
Typically, a vehicle is selectively slowed or stopped (i.e., braked) by the use of brake assemblies which selectively and frictionally engage the wheels of the vehicle, effective to slow or stop the vehicle. While these assemblies do selectively brake or slow the vehicle, relatively large amounts of energy are lost in the form of heat as the vehicle is braked or slowed. Moreover, it is desirable to substantially prevent or reduce the likelihood of having the rear brakes become fully engaged before the front brakes achieve the same state or condition (e.g., to reduce the likelihood of premature rear brake engagement).
A second braking approach, referred to as xe2x80x9cElectronic Brake Force Distributionxe2x80x9d or EBD, often utilizes anti-lock braking or ABS assemblies, sensors, and values to reduce the likelihood of premature rear brake engagement by electronically and dynamically controlling the amount of braking provided by the rear and front brakes. Other more typical approaches are also used to achieve this desired braking distribution, such as by the use of a passive hydraulic proportional valve assembly. The anti-lock braking system and these other assemblies may be jointly referred to as brake distribution assemblies since they each use a dynamically created force distribution pattern which may be expressed in terms of force, torque, or power to allow a vehicle to be selectively braked in a distributive manner.
Regenerative type braking desirably and non-frictionally slows or stops the vehicle while concomitantly allowing electrical charge, or other forms of energy, to be created and stored for later use, thereby improving the overall vehicular operating efficiency while allowing the vehicle to be selectively braked. While regenerative braking is becoming more widely used, the combination of regenerative type braking and the previously delineated anti-lock or distributive braking approaches, although highly desirable, are not used since the brake distribution profiles created by these brake distribution assemblies are not modified to account for the braking effects of the regenerative braking assemblies and, as such, the combination may not provide the desired braking.
The present invention overcomes these drawbacks and provides a braking system which utilizes both regenerative and anti-lock or distributive type braking strategies and assemblies in a manner which allows for regenerative energy recovery and which allows a vehicle to be selectively braked in a desired manner while providing for the benefits associated with diverse types of braking strategies to be employed within a vehicle.
A vehicular braking system is provided which overcomes some or all of the previously delineated drawbacks of prior vehicular braking systems and strategies. The vehicular braking system selectively utilizes both regenerative braking and frictional braking in a manner which allows a vehicle to be selectively slowed or stopped.
According to a first aspect of the present invention a vehicular braking assembly is provided. Particularly, the assembly comprises a first regenerative braking portion; and a second frictional braking portion.
According to a second aspect of the present invention a method is provided for braking a vehicle. Particularly, the method includes the steps of requesting a certain amount of braking, fulfilling at least a portion of the certain amount of requested braking by regeneratively braking the vehicle, and frictionally braking the vehicle according to a certain distribution pattern in the event that only a portion of the certain amount of requested braking was provided by the regenerative braking, thereby fulfilling the request.
According to a third aspect of the present invention a method is provided for operating a vehicle of the type having a first pair of wheels which are operatively disposed upon a first axle, a second pair of wheels which are disposed upon a second axle, a motor which is coupled to the first axle and to a battery, the motor and battery cooperatively and selectively providing a certain amount of regenerative braking, the method comprising the steps of: creating a plurality of relationships, each of the plurality of relationships having a respective first value which is representative of a unique amount of braking of the first axle and a respective second value which is representative of a unique amount of braking of the second axle; generating a brake request signal which represents a certain amount of desired vehicular braking; using the brake request signal to select one of the plurality of relationships; comparing the first value of the selected one of the plurality of relationships with the certain amount of regenerative braking; causing a first amount of braking to be applied to the first axle and a second amount of braking to be applied to the second axle when the first value is larger than the certain amount of regenerative braking and causing a third amount of braking to be applied to the first axle and a fourth amount of braking to be applied to the second axle when the first value is smaller than the certain amount of regenerative braking.
These and other features, aspects, and advantages of the present invention will become apparent from a reading of the following description of the preferred embodiment of the invention and by reference to the following drawings.